I. Field of the Invention
The present invention relates generally to a system and methods aimed at surgery, and more particularly to system and methods for testing the neuromuscular blockade level in a patient prior to conducting nerve tests aimed at detecting pedicle breaches, nerve proximity, nerve direction, and nerve pathology.
II. Discussion of the Prior Art
Despite ongoing advances in surgical methods, neurological impairment remains a serious concern during various surgical spine procedures. The misplacement of a pedicle screw or inadvertent contact between a surgical instrument and nerve during surgery may result in undesirable consequences, including pain, necessitation of revision surgeries, nerve damage, and a possible loss of muscle function. To avert such consequences, surgeons are increasingly relying on systems and methods that capitalize on the knowledge that electrically stimulating a nerve should result in detectable muscle activity.
While these existing EMG systems are significant advancements within the art, proliferated use of neuromuscular blocking agents (muscle relaxants) during surgery present certain challenges with the use of these systems. More specifically, surgeons must wait for a period of time to allow the neuromuscular blocking agents (NMBA) to wear off before initiating a nerve test, which increases surgery time and overall cost. NMBAs generally inhibit the neuromuscular pathway by binding to acetylcholine receptors on the postsynaptic membrane and hence, decrease neuromuscular transmission (transfer of a motor nerve impulse into the muscle) relative to the number of receptors occupied at a given time. This inhibition of the neuromuscular pathway is commonly referred to as neuromuscular block or blockade (NMB). If the neuromuscular pathway is sufficiently blocked, stimulation of a nerve will not result in the otherwise expected contraction of the corresponding muscle. NMB is a necessity during many surgical procedures in order to maintain a certain level of muscle relaxation, however, as mentioned it requires the surgeon to wait for the NMB to wear off prior to initiating a nerve test. If the nerve test is conducted too soon the muscle may fail to contract upon stimulation of the nerve and the stimulation current level at which the nerve is stimulated will appear to be higher than it truly is. This may create, in effect, a false positive wherein the surgeon may believe, for example, a pedicle wall has not been breached or a nerve farther from an instrument than it really is because of the erroneously high stimulation level detected.
The amount and metabolic rate of NMBA may vary from procedure to procedure and person to person. In addition, the present systems retain their effectiveness up to a certain level of NMB. Together this makes it difficult to determine when precisely nerve testing functions regain their effectiveness and surgeons must wait longer than necessary to ensure accurate results, which results in additional surgical time and increased costs. Being able to assess the neuromuscular pathway prior to initiating nerve testing would reduce the amount of waiting time needed and would thus represent a savings in time and costs to both the surgeon and patient.
Neuromuscular pathway testing is currently performed by specialists (neurophysiologists) trained in assessing the neurophysiologic information graphically represented on traditional EMG systems. While these individuals are oftentimes exceptionally skilled and highly trained, there exists the potential for human error on their part in reading and/or monitoring such traditional EMG systems. Moreover, the need for the neurophysiologist to assist in a surgical case adds complexity and challenges in scheduling surgical procedures, in that the schedules of both individuals need to coincide for them to work together. This may disadvantageously cause a patient to wait, while experiencing pain and/or other issues, for the scheduling conflicts of the surgeon and neurophysiologist to resolve. Because the neurophysiologist performs the actual neuromuscular pathway testing, there exists the potential for communication gaps to occur between the surgeon and the neurophysiologist such that the neuromuscular testing may not be conducted as desired by the surgeon. Also, with the attendant activity in the operating room (as well as other operating rooms where the neurophysiologist may be working), the possibility exists that the neuromuscular pathway testing may not be conducted in the desired manner based on inattentiveness of the neurophysiologist.
Based on the foregoing, a need exists for improved systems and methods for surgeon-directed nerve testing during surgery, and in particular a need exits for improved systems and methods for combining neuromuscular pathway assessment and nerve testing capabilities, all being performed by the surgeon. The present invention is directed towards fulfilling these needs.